Best Environmental Management Practice in THE...

Best practice 5.7 – Rainwater and grey water recycling

Best Environmental Management Practice in THE TOURISM SECTOR

Rainwater and grey water recycling

This best practice is an extract from the report Best Environmental

Management Practice in the Tourism Sector.

Find out about other best practices at www.takeagreenstep.eu/BEMP or download the full report at http://susproc.jrc.ec.europa.eu/activities/emas/documents/TourismBEMP.pdf

5.7

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Best Environmental Management Practise in the Tourism Sector 2

5 5.7 Rainwater and grey water recycling

Description

A Some water applications in buildings, such as toilet flushing and irrigation, do not require the use of

potable water. These applications can be responsible for a large share of total water use. Landscaped

grounds were found to be the most important determinant of water use efficiency across Hilton hotels.

Across Scandic hotels each m2 of landscaped ground was statistically associated with an additional 88

L per year of water consumption (Bohdanowicz and Martinac, 2007). Thus, the use of water recycled

from on-site rainwater or grey water collection systems can considerably reduce demand for potable

water from the mains supply.

Rainwater collection systems divert rainfall water into storage tanks. Run-off systems can be installed

on roofs and other impervious surfaces. The harvested water can be used for non-potable demand

such as toilet flushing, washing machines, irrigation, cooling towers or general cleaning purposes.

Thirty-five percent of new buildings built in Germany in 2005 were equipped with rainwater

harvesting systems (EC, 2012), and about 100 Accor hotels have been installed with rainwater

recovery tanks to supply irrigation or car washing applications.

Grey water is the term used to describe waste water from activities such as bathing, showering,

laundry, dishwashers, and excludes 'black water' from toilet flushing. Grey water may be collected

and reused for non-potable water applications such as toilet flushing and irrigation by the installation

of separate waste water drainage systems for toilets and grey water sources.

Although usually too expensive and impractical to retrofit, water recycling systems can be installed at

relatively low cost during construction, and at reasonable cost during major renovations. Smith et al.

(2009) estimate water recycling systems can add 15 % to plumbing system costs during major

renovation. The decision to install rainwater collection systems and grey water recycling should be

based on a cost-benefit assessment that considers economic and environmental criteria, including the

source and scarcity of water supply now and in the future. Water recycling is highly visible to guests,

and may thus be a useful way to convey corporate environmental responsibility. One potential

alternative for enterprises with a high irrigation water demand that can avoid the need for installation

of a separate waste water collection system is the use of all treated waste water for irrigation (section

6.3).

Rainwater collection for irrigation is regarded as a basic good practice measure. Best practice is

considered to be:

installation of a rainwater collection and distribution system for use inside the building

installation of a grey water collection, treatment and distribution system for use either inside or

outside the building.

Achieved environmental benefit EC (2009) estimate that water recycling can reduce water consumption by an additional 10 %, after a

40 % reduction in water consumption achievable from implementation of water efficiency measures.

A rainwater recycling system installed in the 250-room ETAP city-centre hotel in Birmingham, UK,

saves up to 780 m3 of potable water per year (5 % to 10 % of consumption). This saving equates to

about 6 % of best practice water consumption for this size of hotel (after implementation of all other

water efficiency measures).

NH Campo de Gibraltar hotel substitutes 20 % potable water with filtered and treated grey water from

showers, used to flush toilets.



There are some cross-media effects associated with rainwater collection and grey water recycling (see

below). The overall environmental benefit will be highest where local (perhaps seasonal) water

shortages exist, and where water is imported from other areas or desalinated. In such areas, modest

reductions in water consumption may lead to significant reductions in water stress (with associated

benefits, including for biodiversity), and/or energy requirements for desalination.

Appropriate environmental indicator Indicators

The most relevant indicators of water recycling implementation are:

installation of a rainwater recycling system that supplies internal water demand

installation of a grey water recycling system that supplies internal or external water demand

quantity of rainwater and grey used, m3/yr

percentage of annual potable water consumption substituted with recycled rain- or greywater

In areas where seasonal water scarcity is a problem, particularly as a consequence of tourism demand,

seasonal indicators may be relevant – e.g. water consumption per guest-night during peak season, or

percentage reduction in consumption achieved over the peak season.

Benchmarks of excellence

So far, there is little information on specific water savings achievable through the implementation of

this BEMP, which may vary considerably depending on factors such as climate. Therefore, the

following benchmark of excellence represents best practice for this technique.

BM: installation of a rainwater recycling system that supplies internal water demand, or a

grey water recycling system that supplies internal or external water demand.

Best practice in this technique may also be reflected in conformance with the benchmark for potable

water consumption in section 5.1 (i.e. ≤140 L per guest-night for fully serviced hotels and ≤100 L per

guest-night for other types of accommodation).

Cross-media effects Reused rain water can have a higher energy and carbon footprint than mains supply water owing to

infrastructure and pumping requirements. The carbon footprint of a domestic sized rainwater

harvesting system over 30 years has been estimated at approximately 800 kg CO2 eq. However, this is

minor compared with total household carbon emissions from energy use, which can be 100 times

higher.

Rainwater reuse systems essentially bypass the natural water cycle. Where drainage water would

otherwise soak into the ground, and where groundwater levels are locally declining, and where water

is supplied from a (nearby) area with greater water availability, widespread rainwater harvesting could

exacerbate local water stress. Such situations are unlikely, however. On the contrary, widespread

rainwater harvesting could reduce flooding risk during high rainfall events.

Operational data Run-off water quality

Contaminants in roof run-off water include organic matter, inert solids, faecal deposits from animals

and birds, trace amounts of metals and complex organic compounds. Concentrations vary depending

on roof material, antecedent dry period and surrounding environmental conditions (e.g. proximity

motorways or industrial areas). Leaching of heavy metals such as copper, zinc and lead can present a



problem where these materials are extensively used in roof construction. However, a study of roof

run-off quality in Hamburg, Germany, found that copper, lead and zinc concentrations were well

within World Health Organization drinking standards (Villarreal and Dixon, 2005). The quality of

roof run-off (Table 5.33) is acceptable for domestic uses, especially following basic filtration. It is

possible but usually not necessary to fit a device to rainwater collection systems that diverts the first

flush of run-off water during rain events, containing the highest concentrations of contaminants, to

normal drainage.

Table 5.33: Water quality parameters for 'fresh' and stored roof run-off water

pH BOD COD TOC TS SS Turbidity

mg/l NTU

Roof run-off 5.2 – 7.9 7 – 24 44 – 120 6 – 13 10 – 56 60 – 379 3 – 281

Stored run-off 6 – 8.2 3 6 – 151 – 33 – 421 0 – 19 1 – 23

Source: Villarreal and Dixon (2005).

Run-off water from some surfaces such as car parks can contain relatively high levels of contaminants

such as hydrocarbons and heavy metals from vehicles, and will not be suitable for use indoors. Run-

off water should be tested before deciding to install a recovery system. Where water is not suitable for

indoor use, it may be suitable for irrigation following installation of a first-flush diverter and

appropriate filtration.

Run-off collection system design

Rainwater collection and reuse is a simple process. The necessary components can be easily installed

in a new building at relatively little expense, but are more difficult to retrofit in an existing building.

Extensive plumbing modifications are required to separate the water supply network into two systems

supplying: (i) kitchen taps, bathroom taps and showers supplied by 100 % potable water from the

mains supply; (ii) toilet cisterns, urinals and laundry facilities supplied with rainwater or potable water

depending on availability. Where rainwater is available in sufficient quality and quantity, it may also

be used in showers.

A typical rainwater reuse system comprises the following components.

A standard roof or surface run-off water collection system operating under gravity and diverted into

a storage tank, fitted with a debris screen and filter.

A storage tank with water-level detector, ideally situated underground, into which rainwater is

diverted from standard rainwater collection pipes.

A control unit that sends either mains water or stored rainwater either directly to the distribution

system under pressure, or to a header tank.

A separate pipe distribution system feeding relevant fittings (urinals, cisterns, etc.) with water

supplied either directly under mains/tank-pump pressure or from a header tank.

(Possibly) A header tank with float-operated inlet valves from pumped rainwater and from the

mains water supply, and an outlet valve into the building water supply system.

There are various methods of tank sizing, some of which may be area specific. One guideline is that

the tank should be large enough to hold 18 days of average demand, or five per cent of annual yield,

whichever is lower (Peacock irrigation, 2011). Another guideline is that the tank should be able to

store sufficient water to supply average demand over the longest dry periods (statistically defined

from 30-year climatic data). The yield can be calculated by the following simple equation:



S = (R/1000) x A x RC

S Annual supply m3

R Annual rainfall mm

A Plan area draining into collection pipes m2

RC Run-off coefficient 0 – 1

Annual rainfall varies considerably across and within countries and across years. Climatic average

annual rainfall data should be obtained from the nearest weather station. Area refers to the plan area,

which will differ from the roof area for sloping roofs. UNEP (2009) suggest run-off coefficients of

0.8 – 0.9 for tile roofs, 0.6 – 0.8 for concrete and 0.7 – 0.9 for metal sheets.

Thus, for a concrete roof with a 500 m2

plan area in a region exposed to 1 000 mm annual rainfall,

annual run-off water supply would be 1 x 500 x 0.7 = 350 m3. Applying the 5 % rule, the total

recommended tank capacity would be 17.5 m3. However, strong seasonality in rainfall, in particular

the occurrence of long dry periods, may require larger capacity. The seasonality of rainfall patterns

should be assessed, and tanks may be sized according to the aforementioned dry-period supply rule.

The British Standard code of practice for rainwater harvesting systems (BSI, 2009) recommends a

modelling approach to tank sizing that considers temporal variations in demand and yield, using at

least three years of data, for commercial applications such as tourism establishments. Occasional

overflows are a useful way to clean debris from the tank and maintain water quality. Tanks may also

be sized for stormwater control to reduce the risk of flooding, in which case statistical data on storm

events should be used to specify 'oversized' tanks.

Rainwater system installation

Rainwater collectors such as guttering should be regularly inspected and kept clean of debris,

including leaves. Wire mesh screens may be fitted to gutters to debris entering the system, and it is

recommended to fit a filter to the inflow of the rainwater collection tank. These typically contain a

fine wire mesh of e.g. 0.35 mm, may contain additional micro-filtration layers, and can be self-

cleaning (by periodically applying high-pressure water over the mesh surface to a separate outlet for

debris). A first-flush diverter may be fitted to reduce the concentration of pollutants in the collected

rainwater (Figure 5.35).

Source: UNEP (2003).

Figure 5.35: Float-ball mechanism to divert first flush run-off water

Prefabricated rainwater storage tanks are commercially available in sizes of up to 7 m3 for

underground types and 10 m3 for above-ground types (Bicknell, 2009). It is possible to buy tanks built

in two pieces that are joined together during installation – these can be particularly useful where space

onsite is restricted for installation. Where large storage capacity is specified at the building design

phase, purpose-built concrete tanks may be constructed. Alternatively, multiple pre-fabricated tanks

may be installed in series (see Table 5.34).

Slow percolation via small drainage hole



Table 5.34: An example of a small rainfall collection (above) and storage (below) system, from the

Rafayel Hotel in London



Tanks should be installed underground or in unheated basement areas where the temperature remains

stable and relatively low throughout the year. Buried tanks with an ambient temperature not exceeding

12 ºC are ideal because they restrict biological activity that can otherwise be associated with water

discolouration, and potential health risks (Bicknell, 2009). BSI (2009) recommend a floating

extraction point at 100 mm to 150 mm below the water surface, or alternatively a fixed extraction

point at 150 mm above the base of the tank. Overflow pipes should be at least equal in capacity to

inflow pipes, protected from backflow and vermin, and, where possible, connected to a soak-away

drain.

It is highly recommended to install a meter to measure rainwater use. This will facilitate the

identification of problems, and enable calculation of potable water savings. This system will usually

be incorporated into the control system that controls pumps and regulates the backup (potable) water

supply. The system may also be integrated into a centralised building management system.

Pipework should be clearly identifiable as supplying rainwater, and differentiated from pipework

supplying only potable water. Pipework may be identified by markings inserted during manufacture,

or attached labels. It is recommended that labels be attached at 0.5 m intervals along the pipe, and on

the outside of insulation where this is present (BSI, 2009). Similarly, labels and signs should be

visible at all points of use stating 'non-potable water'.

Frequent inspection of the system and tank water can identify water quality problems, combined with

occasional dip testing of water in the storage tank or cistern, for example in accordance with BS 7592.

Sampling of water quality at the point of use is only required if problems are detected from the

periodic sampling (BSI, 2009). Guideline values for use of collected water to flush toilets in single

site and communal domestic systems are provided by BSI (2009):

escherichia coli number ≤250 per 100 ml

intestinal enterococci number ≤100 per 100 ml

total coliforms ≤1000 per 100 ml.

Grey water recovery

Grey water recovery requires the installation of separate waste water collection systems for: (i)

showers, basins, washing machines, kitchen appliances, swimming pools (grey water); and (ii) toilets

(black water). In fact, separate grey water collection may be restricted to room showers and basisns, in

order to avoid more heavily soiled water from kitchens and laundries.

In its most basic form, grey water recycling requires:

installation of a separate waste water collection system for grey water and black water

basic screening to remove debris

installation of large grey water storage tanks (as described above for rainwater harvesting)

connection to an irrigation system.

It is easy to incorporate a basic heat-exchange process into grey water collection systems, to heat fresh

water entering the heating system. Such a system is described in section 9.3 for a campsite. Use for

indoor activities such as toilet flushing requires installation of a separate supply system as described

for rainwater recycling (above). An example of a system using pool overflow water for toilet flushing

is provided for a campsite in section 9.3. Here, the example of NH Campo de Gilbralter is presented.

The 100-room NH Campo de Gibraltar hotel, in Algeciras, Spain, was opened in 2009 with a novel

grey water recycling system shared with one other NH hotel (Hesperia hotel, in Cordoba). Waste

water is collected separately from basins and showers, treated, and recirculated for toilet flushing,



reducing potable water consumption by 20 %. The sequence of steps is elaborated with reference to

photos in Table 5.35.

Table 5.35: Sequence of steps in grey water recycling implemented at NH Campo de Gibraltar hotel

1. Grey water diversion

An electrovalve controls flow of separated

grey water into the treatment tank depending

on remaining capacity. If full, grey water is

diverted to the sewer.

2. Grey water filtering

A flow sensor located after the electrovalve

activates a dosing system to add hypochlorite

to grey water entering the treatment room for

recovery.

Following hypochlorite dosing, water is

filtered through a mesh screen to remove

debris such as hair. This screen is manually

cleaned, requiring 15 minutes per day. Debris

is collected in a standard waste bin and sent

for disposal.

Filtered water is left to settle in a

sedimentation tank. Sludge from the

sedimentation tank is collected every 15 – 30

days by a tanker.

.

3. Storage

Filtered, settled grey water is directed to a

series of three intermediate and two final

storage tanks.

Filter

Sedimentation

tank



4. Distribution

Stored grey water is pumped to toilet cisterns

throughout the hotel through a clearly labelled

grey water pipe network.

5. Toilet flushing

All toilets in the hotel are flushed using treated

grey water.

CRC (2002) make the following recommendations for the safe reuse of grey water that minimises

potential human health risks (in Australian conditions):

kitchen grey water should not be included as it is highly polluted, putrescible and contains

many undesirable compounds;

grey water should not include waste water from kitchen sinks, dishwashers, garbage disposal

units, laundry water from soiled nappies or wash water from the bathing of domestic animals;

removal of hair, lint, etc. via strainer or filter is necessary to ensure systems do not clog;

blockages and build-up of slime may be avoided by using pressurised systems;

storage of grey water is undesirable due to the potential for the growth of pathogenic micro-

organisms, mosquito breeding and odour generation;

sub-surface reuse is the preferred method of irrigation as surface irrigation is prone to ponding,

run-off and aerosols (see section 9.2);

reuse for toilet flushing should not be considered as it requires a high degree of treatment to

ensure no health risks, toilet staining or biodegradation in cistern.

Health and safety regulations

Safeguards must be in place to prevent the possibility of backflow of collected non-potable water into

the main supply system. The most rigorous safeguard is an air-gap system. Rainwater harvesting and

grey water systems must conform to the European Standard on backflow protection by an air gap

(EN1717). National regulations usually specify backflow protection requirements applicable to

rainwater or grey water recycling systems. For example, in the UK rainwater harvesting systems that

involve mains supply top-up must comply with section 5 of The Water Supply (Water Fittings)

Regulations 1999 dealing with backflow protection to protect mains water – this requires an air gap



with an unrestricted discharge between the incoming mains water and the recycled water ('a non-

mechanical backflow prevention arrangement of water fittings where water is discharged through an

air gap into a receptacle which has at all times an unrestricted spill-over to the atmosphere': UK

Governemnt, 1999). A tundish (Figure 5.36) is an appropriate spill-over arrangement (Bicknell,

2010).

Figure 5.36: Basic tundish device

Applicability The installation of rainwater and grey water recycling systems is applicable to all new buildings.

Retrofitting such systems to existing buildings is expensive and impractical unless the building is

undergoing extensive renovation.

Where waste water is treated on site and there is a high demand for irrigation water, treatment and use

of all waste water for irrigation may be a more efficient option than separation and reuse of grey

water.

Economics The costs of equipment of water recycling facilities are high and the payback period is longer than for

other water efficiency measures. A 14-year payback period was calculated for installation of rainwater

recovery in the ETAP Birmingham city centre hotel (Accor, 2010). Therefore, this option should be

applied after other more cost-efficient measures have been taken (see sections 6.2 6.6).

Grey water recovery systems require separate pipework and are therefore difficult to retrofit. Payback

periods vary from 2 to 15 years depending on the type of system and the cost of potable water saved

(ITP, 2008). Relatively high maintenance costs, of EUR 2 000 to EUR 3 000 per year, were also

reported for the NH Campo de Gibraltar hotel, offsetting some of the 20 % reduction in the annual

water bill.

Governments may provide financial incentives for the installation of water recycling systems, such as

grants or tax rebates. In the UK, the Enhanced Capital Allowance scheme allows businesses to offset

installation costs for water recycling systems against tax in the year of installation.

Driving force for implementation The two primary objectives for implementing water recycling schemes are to: (i) reduce water

consumption; (ii) reduce waste water volume. The driving forces behind these include water and

waste water service charges (above) and CSR or green marketing (water recycling systems are highly

visible indicators of environmental responsibility). Increasingly, national regulations are encouraging

Overflow

pipe

Tank

inflow

Mains pipe

Valve (level-

detector operated)



the installation of water recycling systems. In the UK, the following main regulatory drivers apply

(Bicknell, 2010).

The Code for Sustainable Homes encourages builders to install rainwater harvesting in new-

builds.

Part G of the Building Regulations (April 2010) sets a mains water consumption standard of

125 litres per head per day.

Councils give expeditious and sympathetic handling of planning permission to applications

which include rainwater harvesting.

The Flood and Water Management Bill (April 2010) suspended the automatic right to connect

to a sewer, encourages rainwater harvesting to help alleviate flood threats, and gives water

boards greater powers to ban the use of hosepipes for outdoor water use during water shortages.

In addition, building standards such as BREEAM (BRE Environmental Assessment Method) contain

requirements or award optional points for water conservation measures including water recycling, and

governments may offer financial incentives (see above).

Reference organisations

Over 100 hotels within the Accor group have rainwater recovery systems in use. The 250-room

ETAP city-centre hotel in Birmingham, UK, installed a rain-water recovery system in 2007 that

supplies toilet cisterns in 90 rooms and saves up to 780 m3 of water per year. Potable water

consumption is reduced by between 5 % and 10 % (Accor, 2010).

The NH Campo de Gilbralater hotel recovers grey water from showers and basin for toilet

flushing, as described in Table 5.35 above.

The Uhlenköper Campsite in Germany uses water from the natural swimming pool to flush

toilets in the adjacent washroom.

Kühlungsborn camping park uses grey water from showers and basins in the washroom for

irrigation, following heat recovery described in section 9.2.

Basic practice is demonstrated by the 14-room Strattons hotel and restaurant in Norfolk, UK.

Rainwater storage capacity of 15 900 L was installed, comprising one large 10 000 L tank, a

smaller 1 100 L tank, and 12 x 400 L water butts (Envirowise, 2008). This water is used to

irrigate the 0.4 hectare grounds that include a fruit and vegetable garden cultivated to supply the

on-site restaurant. An additional 2 000 L of grey water per week are recovered from restaurant

and kitchen operations and used in the garden.

Another example of basic practice is the Rafayel Hotel in London, where rainwater is collected

from the building roof and car-park-cover (Table 5.34, above) for irrigation of planted areas.

References

Accor, Accor best practice – waste water recovery: ETAP Hotel in Birmingham, UK, Accor,

2010, Paris.

Aquacycle 900, greywater recycling homepage accessed December 2011:

http://www.freewateruk.co.uk/greywater-Ia.htm

Aquavalor, homepage accessed November 2011: http://www.aquavalor.fr/



Bicknell, M.A., Rainwater Harvesting: use of mass-produced underground storage tanks and

the Rain Director® in multi-home developments and commercial buildings,

RainWaterHarvesting, 2009, Peterborough.

Bicknell, S.A., Rainwater Harvesting: Regulatory Aspects, RainWaterHarvesting, 2010,

Peterborough UK.

BSI, BS 8515:2009. Rainwater harvesting systems – code of best practice, BSI, 2009, UK

CRC, Water management and sustainability at Queensland tourist resorts, CRC, 2002,

Queensland Australia. ISBN 1 879985 36 0.

EC, Study on water performance of buildings, DG ENV, 2009, Brussels.

EC, technical report on best environmental management practice in the building and

construction sector, EC IPTS, 2012, Seville. Current draft available at:

http://susproc.jrc.ec.europa.eu/activities/emas/construction.html

Envirowise, Resource efficiency at a small hotel, case study CS 616R, Envirowise, 2008,

Didcot UK.

Free Water (UK) http://www.freewateruk.co.uk/

Imteaz, M.A., Shanableh, A., Rathman, A., Ahsan, A., Optimisation of rainwater tank design

from large roofs¨a case study in Melbourne, Australia, Resources, Conservation and Recycling

55, 2011, pp. 1022 – 1029.

ITP, Environmental Management for Hotels, ITP, 2008, London UK.

NH Hoteles, Proyecto de monitorización de consumos de agua, NH Hoteles, 2011, Madrid.

Peacock Irrigation, Rainwater harvesting systems, Peacock irrigation, 2011. Available at:

http://www.peacock-irrigation.co.uk/rainwater.html

Rafayel Hotel, personal communication June 2011.

Smith, M., Hargroves, K., Desha, C., & Stasinopoulos, P., Water transformed – Australia:

Sustainable water solutions for climate change adaptation. Australia: The Natural Edge Project,

TNEP, 2009. Available at:

http://www.naturaledgeproject.net/Sustainable_Water_Solutions_Portfolio.aspx

UK Government, The Water Supply (Water Fittings) Regulations 1999 No. 1148, Her

Majesty's Stationary Office, 1999, UK.

UK Rainwater harvesting association, homepage, accessed December 2011:

http://www.ukrha.org/

UNEP, A manual for water and waste management: what the tourism industry can do to

uimprove its performance, UNEP, 2003, Paris France. ISBN: 92-807-2343-X.

UNEP, Rainwater harvesting in the carribean. RWH Technical Fact Sheet 1A: Calculating the

amount of water you can capture off your roof, UNEP, 2009, Paris France.

Villarreal, E.L., Dixon, A., Analysis of rainwater collection system for domestic water supply

in Ringdansen, Norrköping, Sweden, Building and Environment, Vol. 40 (2005), pp. 1174 –

1184.



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How to cite this document

This best practice is an extract from the report Best Environmental Management Practice in the Tourism

Sector to be cited as: Styles D., Schönberger H., Galvez Martos J. L., Best Environmental Management

Practice in the Tourism Sector, EUR 26022 EN, doi:10.2788/33972.

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